Capacitive touch screens have been widely applied in consumer electronics such as smart phones and Mobile Internet Devices (MIDs). Generally, a capacitive touch screen is operated by touching it with a finger, which is natural for humans. However, on some occasions, especially when one wants to write, finger touching is not suitable, because, for example, touching a capacitive touch screen with a finger does not provide good accuracy, cannot be performed on a relatively small surface, and does not permit signature signing.
Moreover, since humans are accustomed to writing with a pen after the long history of writing, and capacitive touch screens become the most prominent touch screen products currently on market, touch styluses compatible with capacitive touch screens are in urgent need. However, the touch styluses commercially available function the same as a human finger, i.e., touching the capacitive touch screen to change the capacitance of the capacitive touch screen. This method requires a minimum contact area between the touch stylus and the capacitive touch screen to provide a certain interaction strength, which is generally a circular area with a diameter larger than 5 mm, adding a relatively high requirement to the touch stylus. As a result, most styluses commercially available have a tip larger than 5 mm, making the way that they operate almost identically to a finger. Hence, these touch styluses have the same problems as a human finger, i.e., they cannot be used on a relatively small surface or to sign a signature.
In the prior art, there is another type of touch stylus, which has a tip consisting of soft bristles about 1 mm long. These soft bristles are made of an electrically conducting material. When this type of touch stylus touches a capacitive touch screen, the soft bristles are pressed down, creating a larger contact area. However, the soft bristles are independent from each other, with a gap between, thus they cannot contact the capacitive touch screen at every point even when they are pressed down, which lowers the effective contact area and reduces the success rate of operating the capacitive touch screen with the touch stylus.